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Fluid quality sensor

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Fluid quality sensor


An object of the present invention is to accurately detect concentrations of mixtures in a fluid. An internal electrode 23 is disposed on the inner side of an external electrode 22 coaxially with the external electrode 22, and a plurality of points in the length direction of the internal electrode 23 are supported by a casing 21 via supporting members 28a and 28b. The state of a fluid S passing through a passage 26 between the external electrode 22 and the internal electrode 23 is detected based on electrostatic capacitance between the external electrode 22 and the internal electrode 23.

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Inventors: Takashi TSURUTA, Kazuhiro NISHIKAWA, Koichi KUBOTA, Takuto SHIBAYAMA
USPTO Applicaton #: #20120286810 - Class: 324663 (USPTO) - 11/15/12 - Class 324 


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The Patent Description & Claims data below is from USPTO Patent Application 20120286810, Fluid quality sensor.

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FIELD OF THE INVENTION

The present invention relates to a fluid quality sensor for detecting the concentration of a fluid by a capacitive sensing method.

BACKGROUND OF THE INVENTION

FIG. 11 shows a fluid quality sensor of WO2007/019577. In order that a fluid S flowing from an upstream fluid pipe 25 toward a downstream fluid pipe 27 may be detected based on electrostatic capacitance and temperature, a pipe 61 connected to the fluid pipe 25, a pipe 62 connected to the fluid pipe 27, and an intermediate pipe 63 interposed between the pipes 61 and 62 form a fluid path 64. An internal electrode 65 is disposed on the fluid path 64 inside the immediate pipe 63 via a supporting member 66. The intermediate pipe 63 is an external electrode, and the internal electrode 65 is electrically insulated from the immediate pipe 63 by the supporting member 66. A temperature sensor 67 indirectly detects the temperature of the internal electrode 65 with a detector 68 thermally connected to the supporting member 66.

Thus, based on a capacitance value between the intermediate pipe 63 and the internal electrode 65 and a temperature detected by the temperature sensor 67, the state such as the concentration of the fluid is detected.

Further, FIG. 12 shows a fluid quality sensor of Japanese Patent No. 2639753.

Pipes 70 and 71 are joined to each other in a substantially T-shape. A fluid S flows in from an inlet 70a on one end of the pipe 70 and flows out from an outlet 71a on one end of the pipe 71. The other end of the pipe 70 is closed by an electrode inserting member 72. An internal electrode 73 is inserted from the other end toward the one end of the pipe 70. Reference numeral 74 denotes a temperature sensor attached to the outer peripheral surface of the pipe 70.

Thus, based on a capacitance value between the pipe 70 and the internal electrode 73 and a temperature detected by the temperature sensor 74, the state such as the concentration of the fluid S is detected.

DISCLOSURE OF THE INVENTION

However, in the first related art example of FIG. 11, the rod-shaped internal electrode 65 in the fluid path 64 is held at only one point by the supporting member 66, and thus excessive stress is applied on the supporting member 66 according to the flow rate and the viscosity of the fluid S. It is highly likely that the excessive stress applied on the supporting member 66 causes the internal electrode 65 to vibrate or be displaced. In order to avoid the problem, in general, the thickness of the supporting member 66 or a distance between electrodes is increased. However, the increased distance between electrodes inevitably reduces the detection accuracy. Further, the cross-sectional area of the fluid path becomes non-uniform and the flow of the fluid S is disturbed, and thus the detection accuracy becomes unstable in sensing the fluid S with time and small changes in the properties of the fluid S are hardly noticed.

The present invention has been devised to solve the problem. An object of the present invention is to provide a fluid quality sensor capable of detecting the fluid S with high accuracy over a long time despite the flow rate and the viscosity of the fluid S.

A fluid quality sensor for measuring mixture fluid includes: a tubular external electrode disposed on a first passage on an inner side of a tubular casing; an internal electrode having supporting members at both end connected to the casing so as to be disposed on an inner side of the external electrode coaxially with the external electrode, a intake part which are attached to one end of the casing, and have a second passage communicated with the first passage formed between an inner circumference of the external electrode and an outer periphery of the internal electrode; and a outlet part which are attached to another end of the casing, and have a third passage communicated with the first passage, wherein concentration of a fluid passing through the first passage is detected based on electrostatic capacitance between the external electrode and the internal electrode.

Preferably, both ends of the internal electrode are extended along the second and third passages respectively, and cross-sectional areas of the second passage and the third passage are equal to that of the first passage.

Preferably, the both ends of the internal electrode are cone-shaped, and the second and third passages of the intake and outlet parts are tapered along the cone-shapes of the both ends of the internal electrode respectively. Angles of the cone-shapes of the both ends of the internal electrode are 10° to 60°.

Preferably, at least two points in a outer surface of the internal electrode are attached to the casing by the supporting members.

Preferably, first members are attached to both ends of the external electrode, the first members having holes in centers of the first members through which the internal electrode passes and being made of electrical insulators, second members are attached onto outer sides of the first members, the second members having holes in centers of the second members through which the internal electrode passes and being made of electrical conductors, and inner surfaces of the second members and an outer surface of the internal electrode are connected by the supporting members, the first members with the external electrode attached thereto and the second members with the internal electrode attached thereto are inserted into the first passage, and are positioned in a diameter direction of the casing, the intake and outlet parts are attached to the both ends of the casing respectively, so that the external electrode, the internal electrode, the first members, and the second members are located, and the external electrode and the first members, the first members and the second members, and the second members and the adapters are sealed with sealing materials. A temperature sensor is connected to the external electrode.

According to the present invention, the plurality of points of the internal electrode in the direction of the passage are supported by the casing via the supporting members such that the internal electrode is held on the inner side of the external electrode coaxially with the external electrode. Thus, the position of the internal electrode can be precisely retained and high detection accuracy can be secured over a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a fluid quality sensor according to a first embodiment of the present invention;

FIG. 2 is a fabrication process drawing according to the first embodiment;

FIG. 3 is an enlarged cross-sectional view showing the main part of FIG. 2;

FIG. 4 is a cross-sectional view taken along the arrows A-A of FIG. 1;

FIG. 5 is a cross-sectional view taken along the arrows B-B of FIG. 1;

FIG. 6 is a configuration diagram showing urethane foaming equipment in a first example;

FIG. 7 is an input/output characteristic diagram of measurement results of electrostatic capacitance in the first example;



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stats Patent Info
Application #
US 20120286810 A1
Publish Date
11/15/2012
Document #
13466759
File Date
05/08/2012
USPTO Class
324663
Other USPTO Classes
International Class
01R27/26
Drawings
9



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